Well Im kinda in the same boat as you right now. Here is my armory to give you some ideas
The World of Warcraft Armory
The defense cap is 540 for raids, however, it never hurts to go over that.
As far as your hp, you can get the enchant for your chest that adds 250(?) hp. It looks like you need to spend some time doing heroics, grinding up some rep, and buying some emblem gear. Unless threat is a big issue for you I'd switch to the meta gem that I'm using. that's another 320hp and a good deal more armor. Socket your necklace. Hope this helps.